Semiconductors are widely used in integrated circuits for electronic applications, including radios and televisions. Such integrated circuits typically use multiple transistors fabricated in single crystal silicon. Many integrated circuits now contain multiple levels of metallization for interconnections. The need to integrate more functions onto a chip has caused the semiconductor industry to search for ways to shrink, or scale, the size of individual transistors and other devices commonly integrated on a chip. However, scaling devices to smaller dimensions can create a multitude of undesirable effects. One of these effects is an increase in the capacitive coupling between conductors in a circuit. Therefore, it becomes imperative to reduce the RC time constant within today's multi-level metallization systems.
The capacitance between conductors is highly dependent on the insulator, or dielectric, used to separate them. Conventional semiconductor fabrication commonly employs silicon dioxide as a dielectric, which has a dielectric constant of about 3.9. The lowest possible, or ideal, dielectric constant is 1.0, which is the dielectric constant of a vacuum, whereas air has a dielectric constant of less than 1.001.